It was supposed to be a simple day on the firing range. But due to the negligence of a Canadian Forces reservist, it turned deadly tragic, a prosecutor told a Calgary court martial Tuesday.

Anthony Tamburro told a panel consisting of five senior military officer the criminal negligence of Maj. Darryl Watts, then a platoon captain stationed in Afghanistan, was to blame for the death of Cpl. Joshua Baker.

Baker was one of the soldiers under Watts' command on Feb. 12, 2009, when a training exercise went horribly wrong.

That day "was supposed to be just a simple day at the range," Tamburro said, in his opening address to the five-man panel. "It turned out not to be a simple day ... the day ended in tragedy."

Watts, 44, faces six charges in connection with Baker's death, the most serious being manslaughter.

The latter could result in Watts being stripped of his military rank and even imprisoned, should he be found guilty.

Tamburro said the soldiers were training with a live weapon designed to disperse metal balls, similar to Claymore mines used by the U.S. military.

But when the device was detonated, soldiers under Watts' command hadn't been instructed to take proper cover, the prosecutor said.